The type of pathogen and history of the cow should play a role in mastitis treatment decisions.

"You must know the mastitis pathogen to know how to treat it," said Pam Ruegg, extension milk quality specialist from the University of Wisconsin-Madison at the 46th annual American Association of Bovine Practitioners' meeting. She encouraged dairy producers and veterinarians to engage in "watchful waiting," keeping an eye on cows identified with mastitis but postponing treatment until milk is cultured and cow history is studied.

Ruegg explained that mastitis treatment decisions made on farm are often based on the visual detection of inflammation, which is not the detection of infection. By the time swelling appears in a quarter, the cow's own immune system is already working to fight the infection. "In many situations, we are treating cases of mastitis that the immune system has already taken care of," she said.

In fact, many clinical mastitis symptoms are likely to disappear after 4 to 6 days with or without treatment, she noted. Therefore, it is hard to determine whether antibiotic treatment or the cow's immune system resulted in the return to normal milk. It can also be difficult to determine whether clinical symptoms have simply subsided or if a bacteriological cure has been achieved. Milk culturing is a great way to determine what pathogens are being dealt with and what intramammary antibiotic treatment protocol would be the most appropriate.

Reviewing cow-specific factors will help producers make better decisions in regards to mastitis treatment and cure success as well. Cows that had mastitis once are more likely to have another case in the future, Ruegg explained. In one study, cows with mastitis for the first time were seven times more likely to reach bacteriological cure than cows with previous infections. Age has also been associated with reduced clinical response to therapy.

The bottom line? Don't treat all cases the same, said Ruegg. Consider the following take-away messages:

Link culture data to treatment decisions.

Check the medical history of the cow before treatment.

Extended duration of intramammary mastitis therapy should not be used for all cases of mild or moderate clinical mastitis.

Do not administer antibiotics to cows that will not benefit from treatment.

Include your veterinarian in developing protocols and measuring outcomes.

For more information, read Making Antibiotic Treatment Decisions for Bovine Mastitis. (Here is the link: http://on.hoards.com/MastitisTreatment)The author is an associate editor and covers animal health, dairy housing and equipment, and nutrient management. She grew up on a dairy farm near Plymouth, Wis., and previously served as a University of Wisconsin agricultural extension agent. She received a master's degree from North Carolina State University and a bachelor's from University of Wisconsin-Madison.